"Front Matter". In: Organosilanes in Radical Chemistry - Index of

Radical Chemistry on Silicon Surfaces 203
41 +
Br 2
Ph2 Si
SiPh2 Si SiPh2 Ph
45
hν (daylight)
Ph2 Si
Ph2Si Si
Si
Ph
H
Ph
O SiPh2 Ph2Si Si Ph
Si
Ph
47
Br 2, H 2O
Ph2 Si
Ph2Si Si Ph
Si
Ph
Scheme 8.9 Proposed reaction mechanism for the formation of 9,10-disilaanthracene derivative
47
residing on or near the surface became significant. Although the success of
silicon is mainly due to the presence of robust native oxide on silicon surfaces,
much attention is being directed towards the synthesis of an organic monolayer,
which can be modified upon demand for specific requirements. In this section,
we deal with the chemistry of hydrogen-terminated silicon surfaces and, in
particular, with radical reactions that have been found to be the most convenient
methods for organic modification of silicon surface [46,47]. Indeed, the
chemistry can be understood in many cases by analogy with radical reactions
of organosilicon hydrides described in other chapters of this book.
Structural properties of hydrogen-terminated silicon surfaces are of critical
importance for their chemical behaviour. Flat (single crystal) and porous silicon
surfaces are available. The Si(111) and Si(100) orientation of a single crystal are
shown in Figure 8.3 together with porous silicon as examples of silicon hydrideterminated
surfaces [47]. The porous silicon is terminated with SiH, SiH2 and
SiH3 moieties in a variety of different local orientations and environments.
These materials are reasonably stable and can be prepared and manipulated
in air for tens of minutes as well as in a number of organic solvents. However,
on prolonged exposure to air, single crystal silicon becomes coated with a thin,
native oxide that can be removed chemically from Si(111) using 40 % aqueous
NH4F or from Si(100) and porous silicon using dilute aqueous HF. Under
ultrahigh vacuum conditions it is also possible to produce uniform monohydride
H w Si(100) surfaces (see below). It is worth underlining that the monohydride
terminal surface of H w Si(111) resembles (Me3Si) 3SiH. For example,
the Si(111) surface after fluoride ion treatment exhibits a sharp peak at
2084 cm 1 with p-polarized infrared light due to Si w H stretching absorption
46
+
C 60